diff --git a/requirements_py35.txt b/requirements_py35.txt
index bcbdbb2..9f374c1 100644
--- a/requirements_py35.txt
+++ b/requirements_py35.txt
@@ -44,7 +44,7 @@ mistune==0.8.3
 mpld3==0.3
 nbconvert==5.3.1
 nbformat==4.4.0
-nltk==3.3
+nltk==3.4.5
 notebook==5.6.0
 numpy==1.14.5
 pandas==0.23.3